Summary

An understanding of agro-ecosystems is key to determining effective farming systems. Here we report the 21-year study of agronomic and ecological performance of bio-dynamic, bio-organic, and conventional farming systems in Central Europe. We found crop yields to be 20 % lower in the organic systems, although input of fertiliser and energy was reduced by 34 – 53 % and pesticide input by 97 %. Enhanced soil fertility and higher biodiversity found in organic plots may render these systems less dependent on external inputs. Definition of the problem: Soils are well buffered systems and an adaptation of the soil - plant relationship from high-input to low external input farming practices may last decades. For instance, soil nutrient stocks are frequently huge in European soils and a normalisation after conversion to organic low-input systems needs time. Also the adaptation of the soil micro-flora to altered chemical soil conditions presumably occurs only after a prolonged period of time upon conversion from high-input to low-input farming. Therefore, long-term trials are essential to assess the agronomic performance of low-input production systems and a focus should be put on studying the underlying soil processes. Project aims: - to analyse the long-term agronomic performance of a Swiss wheat cultivar under organic and integrated farming systems (continued) - to investigate the interrelations of soil properties and plant growth in different farming systems Experiments: - to perform a system comparison experiment with organic and integrated farming (continued, running since 1978) - to assess soil chemical, physical and biological properties - to determine nitrogen and phosphorus dynamics related processes in the soil-plant –microorganisms - system - to study the soil - plant interface Methodology: Soil microbial biomass analyses, enzyme activities, characterisation of microbial populations (Biolog, PLFA, DNA), assessment of mycorrihizal root colonisation and diversity by molecular tools, isotope tracer and dilution techniques.